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From: "nils.smeds at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/103438] Updated documentation for gcc Optimization
 command line options (sec 3.11)
Date: Fri, 26 Nov 2021 21:42:45 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103438

--- Comment #8 from Nils Smeds <nils.smeds at gmail dot com> ---
(In reply to Nils Smeds from comment #7)
> (In reply to Martin Li=C5=A1ka from comment #6)
> > Lemme take a look.
>=20
> Great, thanks.=20

prefetch-loop-arrays appears to be activated on arm,s390 and i386 at level =
-O3
and higher on platforms that support software prefetch (and in the case of =
i386
also have TARGET_SOFTWARE_PREFETCHING_BENEFICIAL defined). For aarch64 it
appears to get activated for optimization level
aarch64_tune_params.prefetch->default_opt_level and higher when
aarch64_tune_params.prefetch->default_opt_level is defined

See:
gcc/common.opt
gcc/config/arm/arm.c
gcc/config/i386/i386-options.c
gcc/config/aarch64/aarch64.c
gcc/config/s390/s390.c

So it does appear to be a bug in the code path for -Q --help=